1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device including a wiring member provided in an opening or depression such as a contact hole formed in an insulating layer provided between lower and upper wiring metal layers or between a diffusion region formed in a surface of a semiconductor substrate and a metal wiring layer and a recess or groove formed in a surface of an insulating layer. Particularly, the present invention relates to a technique for improving a filling property of a metal deposited by a chemical vapor deposition within a contact hole or groove formed in an insulting layer by controlling a deposition property on a flat surface portion of the insulating layer and a deposition property on an inner surface of the contact hole or groove. The present invention also relates to an apparatus for carrying out such a semiconductor device manufacturing method.
2. Related Art Statement
Recently a semiconductor device has been miniaturized and a size of a contact hole formed in an insulating layer provided between a diffusion region and a wiring layer or between successive metal wiring layers has become smaller and smaller. Therefore, an aspect ratio of the contact hole has been increased. In order to establish an electrical connection by providing a wiring member, i.e. plug within the contact hole, a sputtering method has been widely used, in which a wiring metal is deposited within the contact hole. However, it is rather difficult to deposit the wiring metal in the contact hole having a large aspect ratio. In order to deposit a wiring metal in a contact hole, it has been proposed to utilize a chemical vapor deposition method (CVD method).
The CVD method may be classified into a selective deposition type CVD method and a blanket deposition type CVD method. In the selective deposition type CVD method, there are formed on a substrate surface a non-conductive area (e.g. a surface of an insulating layer formed on a lower wiring metal layer) and a conductive area (e.g. a surface of a lower wiring layer exposed in a bottom of a contact hole) and a wiring metal is deposited selectively on the conductive area. In the blanket deposition type CVD method, an underlying metal film such as a titanium nitride film is first formed on a whole surface of the substrate and then a wiring metal is deposited on the titanium nitride film by the CVD method. In the blanket deposition type CVD method, a sensitivity to a surface condition is low, so that the wiring metal film can be manufactured stably in a mass production. Furthermore, in the blanket deposition type CVD method, a metal wiring layer may be simply formed by patterning wiring metal film and the underlying metal film deposited on the flat surface of the insulating layer surrounding the contact hole.
A typical wiring metal used in the CVD method is tungsten and aluminum. In case of forming a tungsten film by the CVD method, tungsten hexafluoride is used as a source material, and in case of depositing aluminum, an organic aluminum compound is used as a source material. Aluminum is superior to tungsten, because an electric resistance of aluminum is lower than tungsten by about three times so that a wiring member having a lower resistance can be obtained. It should be noted that copper and gold having a lower resistance than aluminum may be also deposited by the CVD method.
As the method of depositing aluminum in a contact hole by means of the blanket deposition type CVD method, the following methods have been proposed.
(1) Use is made of a deposition apparatus including a sputter chamber and a CVD reaction chamber which are connected with each other by means of a central wafer handling chamber. At first, on a surface of a substrate in which a contact hole is formed, a titanium nitride film is formed within the sputter chamber. Then, the substrate is transferred into the CVD reaction chamber via the central wafer handling chamber without exposing the substrate to the atmosphere, and an aluminum film is formed on the titanium nitride film by the CVD method using triisobutylaluminum as a source organic aluminum compound material. This known method has been described in U.S. Pat. No. 5,008,217 to Case et al.
The sputter chamber and CVD reaction chamber use different gases at different pressures, so that the deposition apparatus having the sputter chamber and CVD reaction chamber connected with each other via the central wafer handling chamber could not be easily realized. Further, even if such an apparatus is realized, mass production with the deposition apparatus would be difficult.
(2) A titanium nit ride film is first formed by the sputtering method on a surface of a substrate, and then the substrate is introduced into a CVD apparatus in which an aluminum film is deposited by the CVD method using dimethylaluminum hydride as a source material. This method has been proposed by Sugai et al in VLSI International Conference, page 463, 1993.
In this known method, when a substrate temperature is set to such a value that a high deposition rate or speed is obtained, an opening or mouth portion of a contact hole is clogged with aluminum deposited on a flat surface portion of the insulating layer surrounding the contact hole mouth before aluminum is sufficiently deposited in the contact hole. Therefore, in order to fill the contact hole with aluminum sufficiently, it is necessary to decrease the deposition rate by lowering the substrate temperature. Therefore, this method is not suitable for a mass production.
In the above mentioned thesis, there has been proposed to perform a sputter cleaning for the titanium nitride film surface prior to the CVD deposition in order to remove contaminants which are adsorbed on the titanium nitride film in the atmosphere.
(3) A substrate having a titanium nitride film deposited on a surface by the sputtering method is first placed into an etching chamber and a surface of the titanium nitride film is cleaned by using a plasma including chlorine. Then the substrate is transported into a CVD chamber without being exposed to the atmosphere and an aluminum film is formed by a CVD method using dimethylaluminum hydride as a source material. This known method has been described in Japanese Patent Application Laid-open Publication Kokai Hei 7-226387.
In this publication, it has been described that a deposition of aluminum in a contact hole is improved by the cleaning process using chloride, and a surface flatness of the aluminum film deposited on the flat surface surrounding the contact hole is also improved.
The method of depositing tungsten within a contact hole by the selective deposition type CVD method has been described in the following publication.
(4) Use is made of a deposition apparatus including a cleaning chamber and a CVD chamber connected with each other by means of an air-tight passageway. At first, a substrate is placed in the cleaning chamber and a metal surface exposed at a bottom of a contact hole is cleaned by means of plasma containing hydrogen or halogen gas. Then the substrate is transferred into the CVD chamber via the air-tight passageway without being exposed to the atmosphere, and after that tungsten is deposited selectively within the contact hole by the CVD method using tungsten hexafluoride as a source material. This known method has been proposed in U.S. Pat. No. 5,043,299 to Chang et al.
In this method, the plasma cleaning can remove water vapor, oxides and other contaminants that have been deposited in the atmosphere and might prevent the deposition of tungsten.
In case of forming a wiring metal layer, a wiring metal film such as an aluminum alloy film is formed on a whole surface of an underlying insulating layer, and then the metal film is changed into a desired pattern by removing selectively a part of the metal film by means of photolithography and dry etching. However, recently a width of a wiring pattern has become thinner and thinner, so that it has become difficult to perform the dry etching for the wiring metal film. In order to solve such a problem, in U.S. Pat. No. 4,789,648 there has been proposed another known method, in which a thin recess or groove is formed in a surface of an insulating layer and a wiring member is selectively formed within the groove. Also in this case, the CVD method could be advantageously utilized for filling the thin groove with a wiring metal.